Concentration of ores



Juiy 3o, 1929. J. L. TEVENS 1,722,598

CONCENTRATION oF oREs Filed March 26, 1928 INVENToR. .fm/@s L. 5m/ems,

BY Mqf/ M/ Patented July 30, A1929.

UNITED STATES JAMES L. STEVENS, F HAYDEN, ARIZONA.

CONCENTRATION 0F DRES.

Application mea much 2s, 192s. serial No. 264,948.

This invention relates to the concentration of ores, minerals and the like, by llotation, and has for its object the provision of means by which certain metalliferous minerals may 5 be selectively'separated from each other so that the concentrate or concentrates resulting from flotation may contain a relatively large amount of a certain mineral and a relatively small amount of certain other minerals,

whicl1,without means for selective separat-ion,

would tend to form only one concentrate containing all the minerals adapted to separation from the siliceous or other gangue min- -l erals contained in the crude ore.

Crude ores in general contain several minerals (particularl sulphide minerals) which are amenable to otation concentration, and frequently in such cases it is desirable to separate these minerals from each other, producing various concentrates containing a relatively large amount of one particular mineral in each'concentrate. For example, in concentrating a lead-zinc ore it is desirable to produce two concentrates; one containing the major portion of the lead with as little zinc as possible, and the other containing zinc with as little lead as possible. In other cases where ores contain two or more minerals that are amenable to flotation concentration, and where only certain of these minerals are of commercial value, it is desirable to recover only the valuable mineral or minerals and reject as much of the remaining mineral or minerals as possible. For example, many ores contain an excessive amount nf iron in sulphide form, such as pyrite, which if recovnr -d ered with the valuable -minerals would in-y known to the art as selective and diiferential flotation processes. Several methods for carrying out these processes of concentray tion are used in the art of flotation, and several chemical agents are employed to aid such separation. vThe present invention relates to carrying out these processes by means which have been hitherto unknown to the art, and which result in increased simplicity and economy in carrying out these processes, especially when treating the more refractory ores. Broadly this inventioncomprises treating `or conditioning the flotation reagents known as collectors in such a way as to cause them to selectively exert most of their collecting action on certain classes of mineral instead of on the total mineral content of the ore which ordinarily is amenable to flotation.

The collecting agent, according to the present invention, is conditioned by treating same with asubstance consisting of suitable earthy materials, preferably in a finely divided state, such as finely ground rock or a portion of the ore pulp itself, and with water. The collecting agent is mixed with such a substance in the presence of water and given sufficient time of contact to allow proper conditioning. In some cases the conditioning of the reagent may be completed in a few minutes while in other cases several hours contact may be required. The time required for the conditioning treatment may vary with different kinds and quantities of collecting agents and also with various types of substances with which it is conditioned, and different kinds of ores to be concentrated. The amount of time'required for conditioning reagents for treating any particular ore may be easily determined by a few preliminary tests.

After conditioning the collecting agent as described above, the 'substance containing the conditioned reagent is mixed withthe ground ore pulp containing the minerals tobe selectively separated, and the mixture subjected to a flotation operation.

The earthy material used for conditioning the collecting or ilotation agent is preferably a natural earthy material, that is a substance naturally occuring in the earth or derived from such a naturally occurring substance Wit-hout change in the chemical nature thereof. Furthermore, I have found that siliceous earthy materials, such as a port-ion of siliceous material derived from the ore itself, or from other earthy substances, or finely ground siliceous rock, or clay or argillaceous material, may be employed with very successful results in the conditioning of the collecting agent. The term siliceous earthy material as used herein, is understood to include any' material, such as clay, sand, or ore slimes, consisting principally of silica and silicates, and does not indicate that such material may not also include certain other constituents in smaller amounts.

The following is a description of one method of practicing the invention as applied to ores from the Ra Mines, Arizona Division of the Nevada onsolidated Copper' Company. y

For laboratory scale tests, the crude ore as received from the mine Was passed through a small set of rolls which reduced the ore to approximately minus 10 mesh, forming a considerable amount of fines (slimes). Two samples of this product were then made up for the following tests. In further preparation, each sample was mixed with Waterand the suspended slimes removed by decantation.

Each sample of slime pulp was thickened to p about 25% solids. The coarse sands resulting from this classification were ground (wet) in a small pebble-mill to a suitable fineness for otation treatment. Lime, at the rate of 5 lbs. per ton of crude ore, was used to'make the ore pulp alkaline; 50% of the lime being added to the thickened slime pulp and the remainder added-to the sands prior to grinding in the ebble-mill. Upto this point the treatment of) the ore was the same in each case.

For the sake of comparison, the ore in Test `:#:1 of the following tabulation was subjected to oneof the customary methods of treatment. For example, all of the products of the original ore (primary slimes and the ground sands) were combined. The flotation agents (collector and frother) were added to the total ore pulp and the mixture subjected to flotation treatment.

Test #2 of the following tabulation was carried out in accordance with one phase of the present invention. For example, the collecting agent was added to the primar slimes and allowed two hours contact withthis pulp, with intermittent agitation. After this conditioning treatment, the slime pulp was mixed with the ground sand pulp and thev mixture subjected to a froth flotation operation.

Results of tests.

Test $2.- Collecting agent conditioned by Test #L treatment Collecting agent added to total ore pulp just prior to flotation treatment.

with primary slimes for two hours prior to combining with the remainlng rtion ol t a ore ulp for treatment.

Total Cu. Houding Oxide Cu. Total Fe.

Concentrates {Fa Insol. Cu

character due to the copper minerals (chieiiy chalcocite) being deposited in the ore by otation partial replacement of the pyrite; thus the i two important minerals (chalcocite and pyrite) in this particular ore are somewhat intimately combined, i. e., a large amount of the chalcocite occurs as a iilm on the surface of the pyrite. Obviously the grinding of the ore in such cases must be sufficient to free the amount of pyrite that is desirable to reject. However, it is not necessary to grind to a. point of completely liberating the two minerals iny order to effect a very high recovery of the copper mineral and at the same time reject the free or relatively barren pyrite. The conditioned collecting reagent functions readily with the copper minerals and therefore particles of pyrite containing any considerable amount of attached copper mineral are recovered With the copper concentrate.

The process of the present invention hasl amount of free pyrite, a remarkable separation of these minerals from the pyrite was obtained.

The reason for the selective action of the conditioned collecting agent may be due to some chemical or physical changes caused by the presence of the material with which the reagent is treated. It is possible that the collecting agent is absorbed, or otherwise taken up by the earthy substances or minerals with which it is treated, in such a manner as to restrict its collecting action to certain minerals (contained in the subsequently added ore pulp) which have the greatest affinity for such collectors.

While, as above stated, it is preferable that the earthy material used in the conditioning treatment be in a linely divided state, as the effectiveness of the action thereof on the collecting agent is thus enhanced, it is impracticable to state any definite limitation upon the necesary fineness thereof. By way of example, however, it may be stated that the ore slimes used in conditioning treatment in Test #2 above were approximately 87 minus 200 mesh. Considerable variation is also permissible in the percentage by weight which the earthy material used for conditioning bears to the total solid to be subjected to flotation and including such earthy matenial. For exa'mple in Test #2 this relation was about 40%, but this percentage may be varied bctween rather wide limits, for example between 10% and 50%, without departing from the spirit of this invention.

While very satisfactory results have been obtained by carrying out this invention with the use of an alkali-metal Xanthate as the collecting agent which is subjected to the conditioning treatment, any other suitable collecting a ent may be employed. Very good results lave been obtained with a collecting agent known to the art as Texiea. Physically this reagent difers from the alkalimetal xanthates in that it is a liquid compound at ordinary temperatures, and is substantially insoluble in water. I am not aware of the exact chemical composition of this reagent; however, I do know that it is an organic sulphur compound and is sold and commonly known under the trade name given above.

The following table shows the results obtained with Texica when added directly to the tot-al ore pulp as compared with the results obtained by employing this reagent in accordance with the method of the present invention. The method of treating the ore and conditioning the collecting agent as substantially as in the preceding tests, with the exception that the conditioning treatment was conducted for three hours instead of two hours. The same quantity of Texica (approximately .06 lbs. per ton of solids) was used in each test.

Results of tests.

Test t.- Collecting agent conditioned by treating lest 13.- with pri- Collecting mary slimcs agent ad for 3 hours ded to total prior to ore pulp combining just prior with the to llotatien remaining treatment. portion of the ore pulp for flotation treatment.

. Cn. 1. 22 1. 22 Heading nire. 3. 43 3. 43

Cu. 13. S 19.3 Concentrates Fe. 29. 6 28. 2 y gisoL/ible 14. 7 12. 3 u. o 10 11 Tilmgs "ire, 1. o9 2. es

Another collector known to the art as aerofloat and described in United States patent of F. T. )Vliitworth No. 1,593,232, has also been employed; and, while this reagent under certain conditions shows little tendency to function with pyrite, an improvement in grade of concentratesI was obtained by einploying this reagent in accordance with the present invention and in the saine manner as described for Tests #l and #2 as is .shown by the following results. About 0.14 pounds ofpcollector per ton of solids was used in these tests.

As an example of the use of materials other than the clay-like slinics or a portion of the ore itself for the conditioning of the collecting agent, the following procedure was followed in one test. The materials used in the ore mixture for this particular testwere obtained from the following sources.

Boi-nite from Magma Copper Company.

Pyrite from Ray Mines.

Siliceous gangue from Hayden tailings. The siliceous gangue was obtained as a clean sandy material by subjecting a portion of Ray ore, from which the natural clay-like slimes had been removed, to flotation in the presence of a considerable amount of flotation reagent (a butyl Xanthate compound) in order to remove as much of the sulphide mineral as possible. The tailings from this operation consisted of very siliceous material of a sandy nature. These sands were washed several times with fresh water. The material being of a sandy nature, the water after each Washing, was easily removed by decantation and draining. The sandy siliceous material tT Lis obtained was of a solid nature (although not completely dry) and was thus added to a suitably proportioned mixture of the abovenamed sulphides (bornitc and pyrite). The total mixture was placed in a pebble mill and ground in the presence of added Water and lime. After grinding, the pulp was subjected to fiotation where a small amount of fresh reagent was slowly added after most of thc copper' mineral had bcn removed.

In spite of the fact that the siliceous gangue material was Washed well prior to making up the synthetic heading, sufficient collecting agent was retained from the previous iiotation operation to selectively float most of the subsequently added copper sulphides. The collecting agent thus retained with the gangue appeared to be only capable of functioning with the copper sulphides of this ore mixture, i. e., it indicated no tendency Whatsoever to cause the pyrite to float. Thesmall amount of pyrite that discharged with the copper concentrate was either iioated by the action of the added fresh reagent orpulled in a manner similar to siliceous gangue. .It was from this and other similar tests that the peculiar action of the collecting agent, when treated with `certain earthy materials, was noted.

A better understanding of one method of applying the process of the present invention to large scale practice, may be had from the following description of the flow-sheet shown in the accompanying drawing, which illustrates its application at one particular concentrating plant at which this new method or process has been used. The crude ore is crushed (wet) with rolls 1 in closed circuit with screens 2. Lime is added at the roll circuit to protect the rolls, screens, etc. from the corrosive action of certain soluble sulphates contained in the ore. Only a minimum amount of lime is used in this circuit, as larger amounts tend to blind the screens.

Additional lime is added to the screen undersize product to insure a distinct lime alkalinity. The screen undersize flows to a Dorr bowl-classifier 3 where the primary slimes are removed by overflowing the bowl. Additional lime is added to the coarse sands from the primary classifier and the limed sands ground in a ball-mill 4 in closed circuit with a secondary classifier 5. A combination of the products of the primary and secondary classifiers constitutes the feed to the flotation plant.

In the primary classification there is a marked concentration of the sulphides, particularly the pyrite, in the coarse sands which are limed and fed to the ball-mills. Hence the primary slimes are relatively low grade, but the ratio of copper to pyrite is relatively high. ondary classifier contains the major portion of the pyrite from which the copper minerals are selectively recovered in the subsequent flotation operation.

In applying the method of the present invention, the primary slime pulp from clas- Therefore the product of the sec-` sifier 3 flows to a .sump 6 from which it is f pumped to a conditioning tank 7 vfor time treatment. The collecting agent is added to the slime pulp just prior to being pumped to said conditioning tank. After the conditioning treatment, the primary slime pulp is taken from tank 7 and combined with the product of the secondary classifier 5, and the mixed ore pulp subjected to flotation in flotau tion machines indicated at 8.

In carrying out the present invention, any suitable reagent or reagents may be employed, and the ore pulpv containing the minerals which are to be selectively separated may be treated or pre-treated in any suitable manner and with any suitable reagent or reagents which might be used to promote selective separation of such minerals. For example, lime, cyanide, etc. are known to the art as depressors of certain minerals, and such agents are commonly employed to condition ore pulps prior to iiotation treatment. However, I have made very good selective separations of sulphide minerals by applying the method of the present invention without the aid of such reagents or. so-called mineral depressors.

In employing certain of the well known pulp conditioners, the place of introducing such reagents in the mill circuit, in certain cases, is of great importance. For example, at the plant referred to approximately 50% of the total lime used'to condition the ore pulp, is added to the ball-mill feed. The lime added at this point is far more eective in conditioning the mineral or mineral pulp than is apparently the case if this portion of lime is otherwise added to this portion of the ore pulp. The remaining 50% of lime is used to make the primary slime pulp distinctly alkaline.

In cases Where the primary slime pulp, or other earthy or siliceous material used for treating or conditioning the collecting agent, contains soluble salts or other substances which in their natural form would destroy the collecting agent or otherwise render it ineffective for its desired purpose, the pulp containing such material should be treated prior to adding the collecting agent, in such a way as to counteract the deleterious action of such substance. For example, some of the lay ores contain ay considerable amount of sulphate minerals (copper sulphate, iron sulphates, ete.) which tend to concentrate in the primary slime pulp; and in such cases, when employing a collecting agent such as an alkali-metal xanthate, it is necessary to condition the slime pulp prior to ladding and conditioning the xanthate, otherwise the effectiveness of the xanthate might be destroyed. At the plant above referred to the deleterious action of these ore salts, or xanthate, is overcome by neutralizing with lime. Sufficient excess lime and time of contact is allowed to insure proper conditioning prior to adding and conditioning the collecting agent.

The improvements of the method or process of the present invention are not only shown by the provision of means for effecting a better selective separation ot minerals, but also by permitting such separations to be made with increased economy and simplicity. In general, when employing the method of the present invention, the fiotation operation may be conducted in substantially the same manner as is ordinarily employed to produce a bulk concentrate. For example, in cases Where it is desirable to concentrate copper minerals and reject pyrite, the flotation cells may be pulled freely Without danger of recovering an excessive amount of pyrite with the copper concentrate. In other words, it is not necessary to crowd out the pyrite by retarding the flotation cells. In cases Where the fiotation cells are retarded in order to crowd the pyrite out of the copper concentrate, a serious accumulation of pyrite in the cells usually results, especially Where mat-machines are used. The method of the present invention has overcome this condition to a very marked degree, because the air may be freely applied, thus holding the pyrite suspended in the pulp in such a Way that it will continuously discharge with the tailings.

At the concentrating plant above mentioned, the method of the present invention employed in conjunction with grinding the ore in the presence' of lime, has resulted in a marked decrease (approximately 40%) in number of flotation cells required to obtain the usual copper recoveries. This improvement appears to be due to the fact that the conditioned collecting agent functions chiefly with the copper minerals and that the rate of concentration is not retarded by collecting or concentrating a large bulk of pyrite in the flotation froth.

As is seen from the examples of this specification, the method of the present invention provides, primarily, for producing but one concentrate containing a relatively large amount of the desired mineral or minerals to be concentrated. It in any case it is desii-able to produce a second concentrate containing a relatively large amount of other mineral or minerals, this of course may be done by employing any of the Well known methods. For example, certain minerals may be recovered from the tailings produced by the first separation, by merely adding a raw collecting agent and subjecting the pulp to a second flotation operation.

It is understood that the earthy substance with which the collecting agent is treated may be obtained from any suitable source and that the collecting agent conditioned, by treating with such earthy substance may be introduced into the ore pulp containing the minerals to be selectively separated, in any suitable manner. For example, in some cases, the earthy substance (in a pulp or in solid form) containing the collecting agent may be added tothe ore prior to grinding, as described for example in Test #7 above.

It should be. further understood that all earthy substances might not be suitable for treating or conditioning the fiotation agent; therefore, in the appended claims the Words suitable earthy materials are used to include only such earthy substances as are adapted for such purposes.

I claim:

. 1.. The method of effecting a selective separation of certain minerals, by flotation, which comprises adding to an ore pulp containing various minerals, a substance comprising suitable earthy material with which a flotation collecting agent has been mixed, and subjecting the Whole to a froth flotation operation.

2. The method as set forth in claim 1, said flotation collecting agent consisting of a Xanthate.

3. The method set forth in claim l, said flotation collecting agent consisting of an alkali metal xanthate.

4. The method of effecting a selective separation of certain minerals, to separate a concentrate eontaining a relatively large amount of one or more of these minerals, from other mineral or minerals contained in the ore pulp Cil which are also amenable to flotation concentration, which comprises adding to an ore pulp containing all of such minerals, a substance comprising suitable earthy material With which a flotation mineral collecting agent has been mixed and subjected to a conditioning treatment, and subjecting the Whole to a froth flotation operation.

5. The method set forth in claim 4, said flotation mineral collecting agent consisting of a xanthate.

6. The method set forth in claim 4, said flotation mineral collecting agent consisting of an alkali metal xanthate.

7. The method of effecting a selective separation of certain mineral or minerals from other mineral or minerals which are also amenable to flotation concentration, which comprises Yadding to an ore pulp containing such minerals to which a depressing agent has been added to promote such separations, a substance comprising suitable earthy material to which a flotation collecting agent has been added and subjected to conditioning by mixing in the presence of water, and subjecting the Whole to a frothflotation operation.

8. The method set forth in claim 7, said' flotation collecting agent consisting of a xanthate.

9. The method set forth in claim 7 said flotation collecting agent consisting of an alkali metal xanthate.

10. A method of effecting a selective separation of certain minerals from certain other minerals Which are also amenable to flotation concentration, and from an ore pulp containing such minerals to which an alkaline substance has been added to condition said ore pulp, which comprises adding to such a treat- `ed ore pulp, a substance consisting of suitable earthy materials with whieh a flotation collecting agent has been mixed and subjected to conditioning treatment, and subjecting the Whole to a froth flotation operation.

v11. A method of effecting a selective separation of certain minerals from other minerals which are also amenable to flotation concentration, and from an ore pulp containing such minerals which has been prepared for flotation treatment by grinding in the presence of an alkaline substance, which comprises adding to such an ore pulp, a substance consisting of suitable earthy materials with which a flotation collecting agent has been mixed and subjected to conditioning treatment, and

subjecting the Whole to a froth flotation operation.

12. A method of effecting a selective separation of certain minerals from other minerals which are also amenable to flotation concentration, and from an ore pulp containing such minerals which has been prepared for flotation treatment by grinding in the presence of lime, which comprises adding to such an ore pulp, a substance consisting of suitable earthy materials With Which a flotation collecting agent has been mixed and subjected to conditioning treatment, and subjecting the Whole to a froth flotation operation.

13. A method of effecting a selective separation of certain copper minerals from pyrite (or other iron sulphide minerals), and from an ore pulp containing such minerals, to form a copper concentrate containing a relatively small amount of other minerals, which comprises adding to such an ore pulp, a substance consisting of suitable earthy materials with which a flotation collecting agent has been mixed and subjected to conditioning treatment, and subjecting the Whole to a froth flotation operation.

14. A method of effecting a selective separation of certain copper minerals from pyrite or other iron sulphide minerals, and from an ore pulp containing such minerals, to form a copper concentrate containing a relatively small amount of other minerals, which comprises adding to an ore pulp which has been prepared for flotation treatment by grinding the ore in the presence of lime, a substance consisting of suitable earthy materials with which a suitable flotation collecting agent has been mixed and subjected to conditioning treatment, and subjecting the total mixture to a froth flotation operation.

15. The method of separatingl minerals Which comprises mixing a flotation collecting agent with a siliceous earthy materia-l, adding the mixed collecting agent and earthy material to an ore pulp containing a plurality of minerals ordinarily amenable to flotation, and subjecting the mixture to a froth flotation operation to recover a concentrate containing a relatively high proportion of one or more of said minerals and a relatively lower proportion of one or more other minerals.

16. The method of selectively separating minerals from ores which comprises subjecting ore, containing a plurality of minerals ordinarily amenable to flotation, to a grinding operation, separating a portion of the ground material, mixing a flotation agent with the portion so separated in the presence of water, and then adding the mixture to a further portion of ground ore and subjecting the same to a froth flotation operation to produce a concentrate containing a relatively high proportion of one or more of said minerals and relatively lower proportion of one or more other minerals.

17. The method of selectively separating minerals from ores which comprises subjecting ore, containing a plurality of minerals ordinarily amenable to flotation, to a grinding operation, removing therefrom siliceous slimes resulting from said grinding, mixing with said slimes a flotation collecting agent, subjecting the remaining ore to a further grinding operation, adding the mixed slimes`-` and collecting agent to thel remaining ore after such further grinding, and subjecting the entire mixture to a froth iiotation operation to produce a concentrate containing a relatively high proportion of one or more of said minerals and a relatively lower proportion of one or more other minerals.

18. The method of eecting a selective separation of certain minerals, by liotation, which comprises adding to an ore pulp containing various minerals, asubstance comprising a pulp consisting of suitable earthy material and water with which alfiotation collecting agent has been mixed, and subjecting the mixture to a froth flotation operation.

19. The method ofselectively separating minerals which comprises mixing a `flotation collecting agent with a pulp of suitable earthy material and Water, adding the resulting mixture to an ore pulp containing various minerals, and subjecting the same to a froth flotation operation to selectively recover one or more minerals.

20. A method of treating a flotation collecting agent in order to promote selective separation of minerals from ore pulps, which comprises mixing and treating the collecting agent with a substance consisting of suitable earthy material adapted to condition the collecting agent, prior to introducing the collecting agent into the ore pulp containing the p minerals to be separated.

21. A method of treating a flotation collecting agent in order to adapt the same for selective separation of one or more minerals from one or more other minerals which comprises mixing such collecting agent with a siliceous earthy material in the presence of Water, prior to introduction of the collecting agent into the main body of ore pulp containing the minerals to be separated.

22. The method 'of separating minerals which comprises mixing a flotation c0llecting agent with an earthy material, permitting the mixed materials to remain in Contact Jfor a period of time to improve the separating properties ot' said collecting agent, then adding the mixture to an ore pulp containing a plurality of minerals ordinarily amenable to flotation, and subjecting the Whole to a froth otation operation to recover a concentrate containing a relatively high proportion of one or more of said minerals and a relatively lower proportion of one or more other minerals.

' 23. The method of effectingv a selective separation of certain minerals, by otation, which comprises mixing a tiotation collecting `agent with an earthy material, permitting the mixed materials to remain in contact for a period of time to improve the separatingv roperties of said collecting agent, then ad lng the mixture to an ore pulp containing various minerals, and subjecting the Whole to a froth otaton operation.

In testimony whereof I have hereunto sub--y 

